1. Field of the Invention
The present invention relates to a method for forming a laminate, wherein the following steps are continuously conducted: a silane coupling agent treatment step of applying an aqueous solution of a silane coupling agent onto a surface of a metal layer, and drying the resultant applied film to form a silane coupling agent coating; and a lamination step of laminating a resin layer on the silane coupling agent coating.
2. Description of Related Art
Hitherto, in the production of a printed wiring board, the following step is generally conducted in order to improve adhesive performance between a surface of a conductor made of a metal such as copper or copper alloy (metal surface) and an insulating resin of a solder resist, a prepreg or the like: the step of applying an aqueous solution of a silane coupling agent, or the like onto the metal surface, and then drying the resultant applied film (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 5-304361, JP-A No. 6-37452, JP-A No. 7-115275, JP-A No. 7-212039, and JP-A No. 2007-35995).
About the aqueous silane coupling agent solution, it is necessary that the silane coupling agent is first dissolved in water so as to be hydrolyzed, thereby generating silanol groups (Si—OH groups). When the silanol groups react and bond with hydroxyl groups present in the metal surface, a silane coupling agent coating having an adhesive performance onto the insulating resin is formed on the metal surface.
In the silane coupling agent treatment step in the prior art, the aqueous silane coupling agent solution is exchanged whenever metal surfaces as described above are treated for a predetermined period (or a predetermined amount of the metal surfaces is treated). In this way, a fall in the adhesive performance is prevented. In the prior art, however, the timing for the exchange of the solution is decided according to empirical assumptions; therefore, the solution exchange may be performed although the adhesive performance is kept. As a result, much waste is generated against economy and work efficiency. Thus, costs for the production are not easily decreased.
It is known that whether or not the silane coupling agent coating is in a state that the coating can keep the adhesive performance can be checked by knowing the amount of Si present in the surface of the coating from a detailed analysis of the composition of the surface according to X-ray photoelectron spectrometry (XPS).
However, according to the measurement based on XPS, for example, the following problems are caused: (1) The measurement needs to be made under a vacuum condition; thus, much time is required therefor. (2) A machine therefor is expensive. (3) A user of the machine needs to receive training. Thus, the measurement is not easily made, in particular, in order to control silane coupling agent coatings when wiring boards are mass-produced.